Project Summary/Abstract The proposed study aims to develop a brief, valid screening questionnaire to identify individuals at risk for psychosis in non-clinical populations across 3 large, community catchment areas with diverse populations. This is a needed study, as the current screening tools for at-risk psychotic populations have only been validated in clinical and/or treatment seeking samples, which likely do not generalize outside of these specialized settings. The proposed project will administer 3 well-known psychosis risk screeners, as well as additional symptom-based (e.g., depression, anxiety, etc.) and risk-factor based questionnaires (e.g., cannabis and other substance use, a family history of major mental disorders, trauma history) to 6,000 adolescents/young adults in local communities across 3 demographically diverse sites (Philadelphia, Baltimore, and the greater Chicago areas). Based on established cut-off scores from the 3 psychosis screeners, 1,560 subjects deemed as questionnaire higher risk (n=780; QHR) and questionnaire lower risk (n=780; QLR) for psychosis (estimated sample sizes based on pilot data) will be invited to complete semi- structured interviews to determine clinical high risk (CHR) for psychosis status based on the Structured Interview for Psychosis-Risk Syndromes (SIPS) and to assess current/past major mental disorders based on the Structured Clinical Interview for DSM-5 (SCID-5). Based on preliminary data and conservative estimates, we anticipate that 117 of the QHR group will be considered CHR for psychosis. The specific aims are as follows: 1) to determine norms and prevalence rates of attenuated positive psychotic symptoms across 3 diverse, community catchment areas and 2) to develop a questionnaire screener, using both symptom-based and risk factor-based questionnaires, that is validated against the SIPS to identify those at CHR for psychosis in the community. This is the first study in the U.S. to determine the rate of subthreshold psychotic symptoms across diverse non-help seeking samples, which is essential for investigations using dimensional approaches to psychotic disorders. Further, the proposed study will develop an essential screening tool that will identify which individuals have the greatest need for follow-up with structured interviews in CHR studies or clinical settings to determine psychosis-risk status. This tool is will be quite valuable given findings that those who develop psychotic disorders often do not seek treatment until after the onset of the disorder, and that duration of untreated psychosis is associated with more serious clinical outcomes. The proposed study has the potential for major contributions to the early detection and prevention of psychotic disorders.